The bifurcation lesion, particularly in the coronary arteries, is a challenging lesion to treat percutaneously. Each bifurcation lesion has a fingerprint-like uniqueness.
Treatment of bifurcation lesions is currently a topic of much investigation. Unlike most other lesion subsets utilizing bare-metal (BMS) and drug-eluting (DES) coronary stenting, the long-term results, particularly the incidence of restenosis, in either the main or subsidiary (side) branch vessel, after stenting the entire bifurcation are not necessarily better than stenting only the main branch and treating the subsidiary branch with balloon angioplasty. As such, provisional stenting, i.e., main branch stenting and stenting the side branch only when necessary, has been proposed as the preferred technique. Stenting of the side branch may be required in 30-50% of cases. There have been multiple methods proposed to treat bifurcation lesions. None have been shown to be more effective than single stenting alone, although several of these methods have not undergone extensive testing in controlled trials.
In the present specification, we propose a new device, and with it, new techniques to optimize treatment of bifurcation or trifurcation lesions. With this device and method, lesions will be treated more safely and more effectively, both in terms of immediate and long-term results, particularly in regard to the incidence of restenosis.
Conventional wire stents for treatment of blood vessel obstruction are used in conjunction with a catheter having an expandable member, or balloon, and a narrowed distal tip with a single guide wire emanating from the distal tip. In order to position the wire stent, the physician directs a guide wire into the diseased vessel and thereafter guides the catheter to the region of a diseased vessel; after proper positioning of the catheter and wire stent assembly, the physician expands the balloon to a predetermined diameter and thus implants the wire stent within the lumen of the blood vessel apposing it to the vessel wall. The physician may leave the guide wire in place throughout the procedure and thread additional catheters, wire stents, or balloon catheters over the guide wire, and the guide wire allows the physician to return to the same location without additional exploration of the vasculature. The catheter and guide wire are removed following treatment, and the vessel remains patent due to the reinforcement by the expanded wire stent. The wire stent should, in order to properly address the disease that led to the necessity of the treatment, overlay the circumference of the diseased portion and extend to a length beyond the margins of the diseased portion of the blood vessel.
When a catheter with wire stent assembly is used in the treatment of vascular disease in vessels for which there are no bifurcation branches involved in the vessel pathology, a single wire stent can be used with an expected low incidence of complications and with a high rate of confidence that closure will not occur immediately thereafter. However, in situations where the vessel disease occupies not only the main branch but also extends into a side branch, the use of conventional wire stents requires creative stent placement and balloon inflation of the side branch or a combination of more than one stent. In order to address circumstances involving bifurcation vessel disease, many researchers have proposed and designed very specialized and intricate wire stent and balloon assemblies that are designed to fit the bifurcation using angled wire stents or having special designs to allow for use in bifurcation lesions.
One prominent risk when treating bifurcation lesions is the potential for covering or occluding a side branch vessel when placing a wire stent into the main branch. Further, expanding the balloon in the main branch may force the plaque material into and seal the side branch through plaque shifting. Traditionally, when stents are required in both the main and side branches, the guide wire in one of the two branches must be removed and then reinserted through a cell in the previously implanted stent in the other branch. The lack of wire in one branch exposes that branch to closure and inability to rewire the branch or to further vessel trauma from attempts at reentry into the side branch. There is also evidence that implanting a wire stent in a vessel bifurcation can lead to blood flow turbulence which may stimulate growth of atherosclerotic plaque. It is thus an object of the present invention to avoid these complications and to avoid the problems associated with a physician's inability to locate or relocate a side branch or main branch during the procedure.
In order to address the above problems, physicians and researchers have described many methods to treat the bifurcation lesion and have provided a name for each method. Each is designed to use a number of conventional expandable wire stents to repair a bifurcation lesion. Mainly, the procedures are divided into various strategies in deciding which of the two branches to stent first, the main branch or the side branch. Furthermore, the type of balloons to be used varies by preference. Techniques such as the “Skirt,” the “Crush,” the “Culotte,” the “Reverse Crush,” the “Exaggerated Y,” the “Minicrush,” and the “Modified T” reveal the different ways that physicians have attempted to overcome the challenges of treating the bifurcation lesion using creative stent placement and balloon use.
There are four general categories of strategies used in current stenting technology for placing wire stents to treat bifurcation lesions. First is the insertion of a first stent in the main vessel close to the carina, in close proximity to the proximal main vessel. The initial step may also be followed by the opening of the stent towards both branches using the “Skirt” technique, followed by subsequent successive or simultaneous stent placement in one or both distal branches. A second strategy is to stent the proximal main vessel by positioning the stent across the side branch, thereafter reinserting a wire into the side branch and selectively enlarging a cell of the stent at the origin of the side branch vessel by inflating the balloon. Thereafter a stent may be implanted at the origin of the side branch if the origin of the side branch is sufficiently narrowed. The use of “kissing balloons” to fully expand both the main branch and side branch is useful in this second strategy. In order to perform this technique, the guide wire in the side branch must be removed with stenting of the main branch and then reinserted after main branch stenting. Thus, during this period, side branch access has been lost and must be regained, which is usually—but not always—possible. A third strategy is to stent the distal aspects of both branches using either a simultaneous stent placement at the ostium of both distal branches using a “simultaneous kissing stent,” or a repetitive placement of a first stent in the distal main and a second stent in the distal side branch with final “kissing balloons.” Another variant on this strategy is to use a “trouser legs and seat” approach whereby a first stent is placed in the main vessel distal to the carina, a second in the distal side branch, and a last stent in the main vessel proximal to the carina. In this “trouser legs and seat” approach, there is a lack of complete stent coverage of the area immediately surrounding the carina, and this lack of stent coverage may fail to repair the bifurcation to the fullest extent necessary. That is, the conventional wire stent may be placed proximal to, but not entirely occupy, the entire portion of the bifurcation area. This creates opportunity for additional vascular disease or higher blood flow turbulence in the region stimulating further atherosclerotic plaque growth. A fourth strategy is a variant of the previous three and begins by stenting a side branch first. This stent extends into the main branch which is crushed against one wall of the main vessel and a second stent is then implanted in the main vessel across the side branch vessel. Again, the use of final “kissing balloons” after placing a wire back into the side branch is recommended as part of this technique.
There are four common problems associated with the foregoing stent strategies. First is the situation where there is inadequate stent coverage of the diseased area. As discussed above, the “trouser legs and seat” approach is most susceptible to inadequate stent coverage, although each of the strategies may been demonstrated to be susceptible to inadequate coverage even when technique is considered to be optimized.
A second drawback to the foregoing strategies is that there is “too much” metal in certain areas of the bifurcation stenting involved with some stenting approaches. That is, in order to respond to the risks associated with the inadequate stent coverage of some techniques, other techniques by necessity have substantial amounts of metallic stent in certain areas of the bifurcation and in so doing, may change the flow dynamics of the blood in that area. That is, the laminar flow characteristics of a normal bifurcation are altered to increase the amount and area of turbulent flow and may lead to additional vascular disease or accumulation of obstructive plaque in the area and may predispose to acute or subacute stent thrombosis. As it is very desirable to retain laminar flow characteristics to the original vessel structure of the bifurcation, it is important not to oversaturate the bifurcation with too much metal at any particular point within the bifurcation. Furthermore, the use of stents that are designed for “one-shape fits all” may alter the natural bifurcation angle between the main branch and the side branch and increase the severity and area of turbulence in the bifurcation.
A third drawback for each of these procedures is the physician's inability to predictably identify the precise location of the side branch when working with the main branch, or vice versa. Most physicians rely upon visual inspection using contrast or radiological visual imagery to identify the origin of the side branch by tracing possible blood flow. As conventional catheters and wire stent delivery systems have only one distal tip through which only one guide wire extends, the physician must move and reposition the catheter approximating the best place to implant the stent during the process for treating bifurcation lesions. The use of a guide wire in the side branch allows for an approximation of the location of the carina between side and branches.
A fourth drawback, perhaps the most crucial in terms of safety of the procedure, is the need to reposition the guide wire into a side branch after already having placed an expandable steel stent in the main vessel. This maneuver exposes the side branch to lack of guide wire access for part of the procedure. It may be difficult in many lesions because it requires crossing a cell of the wire stent. Further certain angles of the side branch may increase the level of difficulty in crossing and this difficulty may be amplified if the side branch opening (ostium) is severely narrowed or totally occluded. Crossing into the side branch, in fact, may not always be possible, particularly if the side branch becomes occluded during implantation of the main branch stent or if the ostium of the side branch is highly blocked or if the angle between main branch and side branch is highly unfavorable. In situations where the side branch becomes occluded during the procedure, the patient is at risk of additional heart muscle injury to the tissues distal to the occlusion. It is therefore an object of the present invention to reduce the risk of complications by permitting a physician to utilize a single catheter yet manage two guide wires when identification of the main branch and side branch are most efficient, most visual.
The prior art has attempted to address the problems associated with proper placement of wire stents in or around bifurcation lesions. In order to assist the physician in locating the side branch when working on the main branch, there are several prior art efforts to modify stents and devices relative to treatment of bifurcation lesions beyond a mere strategy in the placement of conventional stents in or around bifurcation lesions. For example, U.S. Pat. No. 6,508,836 discloses an apparatus and method for stenting bifurcated vessels that is configured for implanting a wire stent in a side-branch vessel using an angled stent with an angulated portion that corresponds to the angle formed by the side-branch vessel at the main vessel. The apparatus disclosed in the '836 Patent also contemplates the use of a relatively traditional single wire system wherein the catheter has a distal tip from which a single guide wire extends. In addition to this single guide wire emanating from the catheter tip, a second control wire is designed into the apparatus to be used to torque and position the location of the main branch wire stent, such wire stent having an angled portion proximal to the distal tip of the catheter. The stated purpose of the second control wire is to identify the side branch vessel, target the side branch vessel, and use such second wire to torque and position the wire stent, as specifically designed for the main branch vessel prior to expanding the stent within the lumen of the main branch vessel. One clear limitation to the '836 Patent is the requirement that the second control wire emanate from the catheter immediately proximal to the location of the angle design of the main branch vessel stent. That is, the use of a second control wire is coupled with the function of rotating the wire stent into position, and the rotational properties of this design depend upon the second control wire exiting the catheter proximal to the balloon and angled stent surface. The '836 Patent has an alternative embodiment that provides the use of a second control wire that facilitates the positioning of the wire stent having an orifice in the midline region of the main branch wire stent, but this design requires the second control wire to have an exact location relative to a specific wire stent design in order to properly torque or rotate the wire stent into place in the main branch relative to the side branch vessel. Again, the stated purpose of this second control wire is to cooperate with a very specific and tailored wire stent design which allows it to be placed in the main branch of the vessel at the same time the second control wire allows the physician to locate the side branch vessel and rotate the specifically designed main branch vessel wire stent into proper position. In another embodiment of the '836 Patent, the inventor discloses the use of a “Y-shaped” wire stent that is configured around a dual Y-shaped balloon, or expandable member, as described by the inventor. The use of two guide wires as disclosed in the '836 Patent allows a physician to manipulate the very specialized dual balloon Y-shaped wire stent design into position at the bifurcation location. In the embodiments presented in the '836 Patent, all have a single distal tip through which a single wire is threaded, and the essence of the invention is to use guide wires to position highly specialized wire stent designs for use in a main branch vessel.
U.S. Pat. No. 6,955,688 similarly discloses the use of a two guide wire system whereby the single balloon catheter has a first distal tip having one guide wire and a second tip with a second guide wire that projects from the body of the catheter at a position slightly proximal to the balloon or expandable member. This second tip and second guide wire may assist the physician in positioning a stent associated with the first distal tip. In one preferred embodiment of the '688 Patent, this second tip with second guide wire encircled by another balloon may be releasably attached to the first distal tip using a locking ring. The stated alternative embodiment depicts a dual balloon Y-shaped catheter assembly to cooperatively stent a bifurcation. The catheter assembly disclosed in this alternative embodiment of the '688 Patent includes first and second expandable members that are configured to reside side by side (Y-shaped) and which are intended to spring apart for implanting two stents simultaneously. A locking ring is designed to assist in holding the two expandable members together until such time as the physician decides to separate the two for use in differing branches of the vasculature. This locking ring configuration confers a benefit of inserting only one catheter at the commencement of the procedure yet allows the physician to have two guide wires and two wire stents available to the physician to treat the bifurcation lesion. The embodiment disclosed in the '688 Patent has several disadvantages, however, as it has two balloons that are actuated using the single catheter lumen. That is, the physician must necessarily inflate two separate balloons at once, so the physician must be absolutely sure that both wire stents are in the proper place within two different vessels before inflating the balloon. This leaves no room for error, and instead increases the risk of error, as the improper placement of only one of the two stents at once could lead to catastrophic results. The '688 Patent is silent on whether there may be independent inflation means for each of the two tips such that if the physician does not wish to inflate both balloons simultaneously one could do so. The additional components needed to permit independent inflation of either tip would logically increase the diameter of the overall catheter to the same degree as having inserted two separate catheters in succession.
U.S. Pat. No. 6,221,090 B1 discloses a stent delivery catheter assembly designed for use with a torquing member, a tracking guide wire, and a positioning guide wire. The disclosure is for the use of a guide wire and a control wire to allow for rotation of a main branch stent mounted upon such catheter and expandable member into accurate position near the vessel bifurcation. One embodiment disclosed by the '090 Patent reveals a single guide wire at the distal tip of the device and a second control wire that is confined within a complex torquing member apparatus such that the second control wire exits the apparatus at a substantially 90 degree angle from the direction of the catheter and assists the physician in locating a side branch.
The prior art reveals widespread use of a single guide wire catheter system known as the “over-the-wire” and another system known as the “rapid exchange” system. The present apparatus and disclosure is useful in either catheter designs, or a combination thereof. The present invention contemplates the ability of a physician to adapt this system with the most flexibility rather than using a one-size-fits-all main branch wire stent design and a specialized device to help torque or rotate the main branch wire stent into place relative to the side branch. It is further an object of the present invention to allow a physician to remain flexible on which area of the lesion the physician deems is best to stent given the particular characteristics of the bifurcation lesion. That is, the present apparatus is not limited to the requirement that a side branch stent be positioned first. The invention is also not limited to one embodiment or use with only one commercially available catheter system but can instead be used with either existing over-the-wire or rapid-exchange catheter designs.